Hold times refer to the maximum time a sample can be held before laboratory analysis to ensure valid results. Common stormwater parameters and their typical hold times include:

• pH (field): Immediate (analyzed onsite)


• Total Suspended Solids (TSS): 7 days


• Oil & Grease: 28 days (preserved with HCl, cooled to ≤6°C)


• Chemical Oxygen Demand (COD): 28 days (preserved with sulfuric acid)


• Biochemical Oxygen Demand (BOD): 48 hours (cooled to ≤6°C)


• Total Kjeldahl Nitrogen (TKN): 28 days (preserved with sulfuric acid)


• Nitrate + Nitrite-N: 28 days (preserved with sulfuric acid)


• Total Phosphorus: 28 days (preserved with sulfuric acid)


• Metals (e.g., Zinc, Lead, Iron): 6 months (preserved with nitric acid)

Samples must be stored on ice and delivered to the lab within the specified time frame. All sampling should follow EPA 40 CFR Part 136 guidelines and your permit-specific methods.

Many state permits adopt EPA's industrial stormwater benchmark monitoring values. The following are examples for Sector J (Mineral Mining and Dressing) by state:

• Indiana (ISGP): Nitrate + Nitrite-N (0.68 mg/L), Zinc (0.117 mg/L), Lead (0.0816 mg/L)


• Ohio: Iron (1.0 mg/L), Nitrate-N (0.68 mg/L)


• Illinois: Nitrate-N (0.68 mg/L)


• Kentucky: Iron (1.0 mg/L), Zinc (0.117 mg/L)


• Michigan: Nitrate-N (0.68 mg/L), Iron (1.0 mg/L), Total Phosphorus (2.0 mg/L)


• Missouri: Nitrate-N (0.68 mg/L), Zinc (0.117 mg/L), Lead (0.0816 mg/L)


• Pennsylvania: Iron (1.0 mg/L), Aluminum (0.75 mg/L)


• West Virginia: Nitrate-N (0.68 mg/L), Zinc (0.117 mg/L)


• Texas: Iron (1.0 mg/L), Aluminum (0.75 mg/L), Nitrate-N (0.68 mg/L)

Values may differ for other sectors (e.g., A, C, D, E, N) depending on the permit. Always consult your site’s specific authorization letter or general permit language.

Each state may require different analytes based on their industrial stormwater permits. Here's a summary of common analytes required across states surrounding Indiana, plus Texas, Pennsylvania, West Virginia, and Missouri:

• pH (Field): Required in all states


• Total Suspended Solids (TSS): Required in all states


• Oil & Grease: Required in most states


• Nitrate + Nitrite-N: Common in mining and manufacturing sectors


• Total Phosphorus: Required in MI, KY, and mining sites


• Metals (e.g., Zinc, Iron, Aluminum, Lead): Sector-specific in many permits

Refer to your state’s general permit or contact us to confirm site-specific monitoring obligations.